Having the visibility of IK/FK controls being driven by the IK/FK switch?
You can hover on the IK_FK slider &gt; right mouse button &gt; copy as new driver.
Then select a bone of the IK controllers, go to the outliner, enable the visibility icon (screen shape), press dot in the numpad to highlight the selected bone, right click on the visibility icon and choose paste driver.
Repeat for the other IK bones.
Then, for the FK bones you will have to change the driver expression: paste the same on one of the control bones, edit driver and change it from average value to scripted expression and type in &quot;1-IK_FK&quot;.
Then copy this new driver and paste it on the others FK bones.
Note that both IK and FK layers have to be permanently turned on (I've tried to work on layers visibility, but it doesn't work, I don't know why).
For values different from 0.0 and 1.0 both bone chains are visible (which I think is useful).